If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

AGP or NOT

I have a really stupid questions, but what is an agp graphics card and how do I tell if I have one or not. I have an asus V3400TNT card, (I believe PCI, but not forsure) what is the diff? And which is better, ?

AGP stands for Advanced Graphics Port: it is a dedicated port for your graphic card (unlike PCI bus that is a shared media).

It was designed by Intel to allow textures to transfer from the video card to the RAM when there is not video memory enough: a part of the RAM acts as video RAM, hence increasing the video memory.

There are of course drawbacks: the AGP port is still very slow: there many AGP flavours: 1x, 2x, 4x, 8x(??). I don't remember the transfert rate (but it works at 66mhz), but it is slow comparing to the tranfert rate of on-board video memory. One famous example is Falcon4: it draws its 2D cockpit using AGP, resulting in horrible framerate (D3D). Then a patch enables the cockpit to be processed in video memory: the result was +50% framerate.

Since not many CURRENT games use really AGP, I would say it is useless. 3dfx understood this and their AGP vs PCI cards are not different from each other (see Anandtech, I think).

BUT who knows in the future, when games really use AGP and that AGP is much faster than today's standards...

Where is located the AGP port? It is located between the PCI bus and the CPU (as far as I know, AGP is a brown port and PCI bus are white).

If you use an AGP card, you can enter the BIOS and enable the memory amount you want to allocate for AGP (tip: enable 256MRAM whatever the RAM quantity and the AGP card you have).

There is another advantage using AGP: overclocking. When you overclock beyond AGP specs (FSB=133Mhz-&gt;AGP=89mhz=, your video card works faster!!

Well, most peoples PCI system works at 33Mhz (unless overclocked) and AGP works at 66, therefore it's quicker than PCI. An AGP card is allways a little quicker than a PCI one, at least they are in the benches I have seen.

AGP 1x works at 66Mhz, 2x at 133 and 4x at 266, but to be honist the x number doesn't make that much differnce performance wise, because not much uses the AGP transfer system.

PCI cards react better to overclocking. As 1040stf said, when you overclock your FSB it also overclocks the AGPbus. it overclocks the PCI bus too, but AGP runs at PCI clock x2, so the incrase is x2 as well. So if you are overclocked to 133MHz FSB, your AGP bus has gone from 66MHz to 89MHz. Now, if you're running an AGP 2x grafix board, it's gone from 133Mhz normal speed to 178Mhz. Thats starting to get a bit excessive, whereas a PCI card in the same system would be at only 44.5MHz, much closer to specs, less likely to yell.

The AGP 1X clock is 66MHz. You can find its peak throughput by multiplying 66M by 4 (the width of the port) and you get 264 MBPS. The clock rate of AGP 2X is 133MHz which works out to 528 MBPS. AGP 4X uses the 133MHz clock but the transfers are done DDR-style. This results in a 1056 MBPS peak transfer rate. The only problem (besides stability) is that no memory system currently available can supply 1 GBPS. Looking at the results from Sandra indicate peak rates of around 400 to 500 MBPS which is why there is little if any performance gain for AGP 4X over 2X.

You are quite right, 8 Bytes x 133 MHz = 1064 MBPS but I have never seen any systems score that high on tests. I have seen a few get to around 500 M on Sandra but no higher. I have PC133 CAS2 RAM with 4-way interleaving on and that is what I get.